Abstract Detail

Examining the Uniqueness of the Sky Island Pines within Pinus brachyptera using Species Delimitation Based On Multiple Criteria.

At present, there are roughly 17 accepted species of subsection Ponderosae (Pinaceae), however many suspect that there are additional cryptic taxa within the broadly described Pinus ponderosa Lawson and C. Lawson. The sky islands are a collection of isolated mountains in the desert of the American southwest and potentially home to one of these cryptic species. Putatively distinctive morphological features such as predominantly three needles per fascicle lead some to propose that the skyi sland ponderosa are distinct from the ponderosa pine in the Rocky Mountains,as well as being distinct from sympatric P. arizonica. This proposal raises the question whether the name P. brachyptera Engelm. (collected in 1846 near Santa Fe, NM) should be applied to the sky island pines as well as to the ponderosa pines of the southern Rocky Mountains. Chloroplast and Nuclear SSRs were genotyped for about 300 individuals representing 12 populations from the sky islands, the nearby contiguous forests of the southern Rocky Mountains, and more distant sites representing P. ponderosa var. scopulorum Engelm.. We included samples of P. arizonica Engelm.and P. engelmannii Carriere, both sympatric with the sky island pines, to investigate the potential for introgressive hybridization. Using clustering algorithms, we created a visual representation of the genetic variation. We also used Ecological Niche Models based on 19 biologically meaningful climate variables to test if the current geographic distribution of the sky island pines represents an ecological niche that is distinct from the Rocky Mountain habitat. We discuss the usefulness of considering both molecular and ecological criteria to support species delimitation questions: i) are the sky island pines a unique species; or ii) are the sky island pines, as well as the ponderosa pines of the southern Rocky Mountains, a single species?